Dissection of the splanchnic artery unrelated to an aortic lesion is extremely rare. We describe a patient with dissection of the celiac and splenic arteries causing splenic circulatory impairment. A 55-year-old Japanese man was referred to our hospital for left back pain that suddenly occurred 3 days previously and spread to the left flank. He had complicated sleep apnea syndrome well controlled with continuous positive airway pressure, and had been prophylactically taking aspirin (100 mg/day) because of asymptomatic cerebral lacunar infarcts. Contrast-enhanced computed tomography (CT) in the arterial phase revealed dissection from the celiac root extending to the entire splenic artery, the caliber of which was irregularly narrowed, causing malperfusion in the spleen. Because of hemodynamic stability and lack of impending sequelae, the patient was carefully observed with rest, strict blood pressure control, and aspirin administration. One month later, CT revealed restoration of the caliber of the dissected arteries and regression of the organizing false lumen, which confirmed the patient's recovery. Despite the extreme rarity or nonspecific symptoms, splanchnic artery dissection should be considered a potentially life-threatening emergency. This case supports the possible benefit of starting antithrombotic treatment early to prevent thrombotic sequelae such as organ infarction and aneurysmal formation.